Semiconductor light emitting element and semiconductor light emitting device

ABSTRACT

A semiconductor light emitting element, includes: a laminated structure body including an n-type semiconductor layer, a p-type semiconductor layer, and a light emitting layer; a p-side electrode provided in contact with the p-type semiconductor layer; an n-side electrode provided in contact with the n-type semiconductor layer; a highly reflective insulating layer provided in contact with the n-type semiconductor layer and having a higher reflectance than a reflectance of the n-side electrode; and an upper metal layer provided on at least a part of the n-side electrode and on at least a part of the highly reflective insulating layer and electrically connected to the n-side electrode. An area of a region of the n-side electrode in contact with the n-type semiconductor layer is smaller than an area of a region of the highly reflective insulating layer sandwiched between the n-type semiconductor layer and the upper metal layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of International ApplicationPCT/JP2009/065261, filed on Sep. 1, 2009; the entire contents of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

The invention relates to a semiconductor light emitting element and asemiconductor light emitting device.

As for semiconductor light emitting elements such as LEDs (LightEmitting Diodes), light generated in a light emitting layer is directlyextracted to the outside of the element or is extracted to the outsideafter being reflected by various interfaces, electrodes, and the like inthe element.

The shape of an element, the shape of an electrode, and the like areadjusted appropriately in order to increase the light extractionefficiency. However, such adjustment needs to be made while satisfyingvarious requirements of an operating current of the element, the shapeof the electrode for mounting, and light reflex properties. For thisreason, there is a limitation in improvement of the light extractionefficiency by the appropriate adjustment.

JP-A 2007-324585 (Kokai) has disclosed a configuration in which areflective dielectric multilayer film is provided on a side surface anda part of a main surface of a flip chip mounting type semiconductorlight emitting element in order to improve the light extractionefficiency. However, there is room to improve operating properties, thelight extraction efficiency, and mountability such as ease of alignmentof a gold bump.

SUMMARY OF THE INVENTION

According to an aspect of the invention, there is provided asemiconductor light emitting element, including: a laminated structurebody including an n-type semiconductor layer, a p-type semiconductorlayer, and a light emitting layer provided between the n-typesemiconductor layer and the p-type semiconductor layer; a p-sideelectrode provided in contact with the p-type semiconductor layer; ann-side electrode provided in contact with the n-type semiconductorlayer; a highly reflective insulating layer provided in contact with then-type semiconductor layer and having a higher reflectance to lightemitted from the light emitting layer than a reflectance of the n-sideelectrode to the light; and an upper metal layer provided on at least apart of the n-side electrode and on at least a part of the highlyreflective insulating layer and electrically connected to the n-sideelectrode, an area of a region of the n-side electrode in contact withthe n-type semiconductor layer being smaller than an area of a region ofthe highly reflective insulating layer sandwiched between the n-typesemiconductor layer and the upper metal layer.

According to another aspect of the invention, there is provided asemiconductor light emitting device including: a semiconductor lightemitting element; and a mounting component, the semiconductor lightemitting element being mounted on the mounting component, thesemiconductor light emitting element including: a laminated structurebody including an n-type semiconductor layer, a p-type semiconductorlayer, and a light emitting layer provided between the n-typesemiconductor layer and the p-type semiconductor layer; a p-sideelectrode provided in contact with the p-type semiconductor layer; ann-side electrode provided in contact with the n-type semiconductorlayer; a highly reflective insulating layer provided in contact with then-type semiconductor layer and having a higher reflectance to lightemitted from the light emitting layer than a reflectance of the n-sideelectrode to the light; and an upper metal layer provided on at least apart of the n-side electrodes and on at least a part of the highlyreflective insulating layer and electrically connected to the n-sideelectrode, an area of a region of the n-side electrode in contact withthe n-type semiconductor layer being smaller than an area of a region ofthe highly reflective insulating layer sandwiched between the n-typesemiconductor layer and the upper metal layer, the n-type semiconductorlayer being exposed in an exposed region on a side of a first mainsurface of the laminated structure body, a part of the p-typesemiconductor layer being removed in the exposed region, the n-sideelectrode and the highly reflective insulating layer being provided incontact with the exposed n-type semiconductor layer, the p-sideelectrode being provided in contact with the p-type semiconductor layeron a side of the first main surface of the laminated structure body, then-side electrode being provided on the first main surface of thelaminated structure body, the mounting component including a pluralityof mounting electrodes, the first main surface of the laminatedstructure body and the mounting electrodes of the mounting componentbeing disposed to face each other, the upper metal layer beingelectrically connected to one of the mounting electrodes, and the p-sideelectrode being electrically connected to another one of the mountingelectrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic views illustrating a semiconductor lightemitting element according to an embodiment;

FIGS. 2A and 2B are schematic views illustrating a semiconductor lightemitting element according to a first comparative example;

FIGS. 3A and 3B are schematic views illustrating a semiconductor lightemitting element according to a second comparative example;

FIGS. 4A and 4B are schematic views illustrating a semiconductor lightemitting element according to a third comparative example;

FIGS. 5A and 5B are schematic views illustrating a semiconductor lightemitting element according to a fourth comparative example;

FIGS. 6A and 6B are schematic views illustrating another semiconductorlight emitting element according to the embodiment;

FIGS. 7A and 7B are schematic views illustrating another semiconductorlight emitting element according to the embodiment;

FIGS. 8A to 8D are schematic plan views illustrating other semiconductorlight emitting elements according to the embodiment;

FIG. 9 is a schematic cross-sectional view illustrating anothersemiconductor light emitting element according to the embodiment; and

FIG. 10 is a schematic cross-sectional view illustrating a semiconductorlight emitting device according to an embodiment.

DETAILED DESCRIPTION

Hereinafter, embodiments of the invention will be described in detailwith reference to the drawings,

It should be noted that the drawings are schematic or conceptual, andthat a relationship between the thickness and width of each portion, aratio of dimensions between portions and the like may differ from actualones. Moreover, there are differences in dimensions and ratios among thedrawings even when the same portions are shown,

In the specification and the drawings of the application, the samereference numerals are given to the same components as those in thedrawings already mentioned, and detailed description thereof will beomitted as appropriate.

First Embodiment

FIGS. 1A and 1B are schematic views illustrating the configuration of asemiconductor light emitting element according to a first embodiment ofthe invention.

Namely, FIG. 1B is a schematic plan view, and FIG. 1A is across-sectional view taken along line A-A′ of FIG. 1B.

As shown in FIGS. 1A and 1B, a semiconductor light emitting element 110according to this embodiment includes a laminated structure body 10 s, ap-side electrode 50, an n-side electrode 40, a highly reflectiveinsulating layer 60, and an n-side pad layer 41 (upper metal layer).

The laminated structure body 10 s has an n-type semiconductor layer 10,a p-type semiconductor layer 20, and a light emitting layer 30 providedbetween the n-type semiconductor layer 10 and the p-type semiconductorlayer 20. The light emitting layer 30 has a multiple quantum wellstructure, for example.

The p-side electrode 50 is provided in contact with the p-typesemiconductor layer 20. The n-side electrode 40 is provided in contactwith the n-type semiconductor layer 10.

The highly reflective insulating layer 60 is provided in contact withthe n-type semiconductor layer 10. A reflectance to light (emittinglight) emitted from the light emitting layer 30 of the highly reflectiveinsulating layer 60 is higher than a reflectance to an emitting light ofthe n-side electrode 40. The n-side pad layer 41 is provided on at leasta part of the n-side electrode 40 and at least a part of the highlyreflective insulating layer 60 and electrically connected to the n-sideelectrode 40.

For example, the n-type semiconductor layer 10 of the laminatedstructure body 10 s is provided on a substrate 5 made of sapphire, forexample, via an AlN buffer layer. The light emitting layer 30 isprovided on the n-type semiconductor layer 10, and the p-typesemiconductor layer 20 is further provided on the light emitting layer30.

Then, in the semiconductor light emitting element 110 of a specificexample, the n-side electrode 40 and the p-side electrode 50 areprovided on a first main surface 10 a of the laminated structure body 10s.

In other words, in a region (a exposed region) where a part of thep-type semiconductor layer 20 and a part of the light emitting layer 30on the first main surface 10 a side of the laminated structure body 10 sis removed by, for example, etching, the n-type semiconductor layer 10is exposed, and the n-side electrode 40 and the highly reflectiveinsulating layer 60 are provided on the n-type semiconductor layer 10 inthe region (in the exposed region). Then, the p-side electrode 50 isprovided on the p-type semiconductor layer 20 of the first main surface10 a.

A material having ohmic properties to the n-type semiconductor layer 10is used for the n-side electrode 40. For example, a Ti/Al/Ni/Aulaminated film can be used for the n-side electrode 40. The n-sideelectrode 40 becomes an ohmic contact region on the n-type semiconductorlayer 10 by performing a sintering treatment. Note that, the thicknessof the TI/Al/Ni/Au laminated film is 300 nm, for example.

Note that, the reflectance to the emitting light of the n-side electrode40 obtained by sintering the Ti/Al/Ni/Au laminated film is comparativelylow, and is approximately 10%, for example. However, ohmic contactproperties to the n-type semiconductor layer 10 are good. In otherwords, the material used for the n-side electrode 40 is selected byplacing importance on electrical properties while the reflectance of then-side electrode 40 to the emitting light emitted from the lightemitting layer 30 is less demanded.

Moreover, silver or a silver alloy can also be used for the n-sideelectrode 40. In other words, as described later, when a crystal formedon a single-crystal AlN buffer layer is used as the n-type semiconductorlayer 10, an impurity density in the contact layer of the n-typesemiconductor layer 10 can be increased, and lower contact resistanceand good ohmic properties can be obtained. Thereby, silver or a silveralloy, which usually has higher contact resistance and poor ohmicproperties while having a higher reflectance, can be used as the n-sideelectrode 40.

On the other hand, a material and configuration having a higherreflectance to the emitting light emitted from the light emitting layer30 are used for the highly reflective insulating layer 60. In otherwords, the reflectance of the highly reflective insulating layer 60 tothe emitting light is relatively higher than that of the n-sideelectrode 40.

The highly reflective insulating layer 60 can include a plurality ofdielectric films alternatively laminated and having a differentrefractive index from each other, for example. Thereby, the reflectanceto the emitting light can be increased.

The highly reflective insulating layer 60 is provided immediately belowthe n-side pad layer 41 and in a region where the n-side electrode 40 isnot formed, for example.

Then, the n-side pad layer 41 is provided on the n-side electrode 40.The n-side pad layer 41 is electrically connected to the n-sideelectrode 40 and further covers at least a part of the highly reflectiveinsulating layer 60. In the specific example, the n-side pad layer 41covers all over the n-side electrode 40 and the highly reflectiveinsulating layer 60.

The n-side pad layer 41 is a portion serving as a pad for conductingcurrent from the outside to the n-type semiconductor layer 10. In otherwords, a connecting member such as a gold bump and a bonding wire isprovided in the region of the n-side pad layer 41.

For the n-side pad layer 41, a material and a configuration can be usedin which adhesion to the highly reflective insulating layer 60, adhesionto the connecting member such as a gold bump and bonding wire,resistance against diffusion of various elements included in theconnecting member, resistance against increase in temperature during amounting process to the connecting member and the like, for example, arehigher than those of the n-side electrode 40. For example, the n-sideelectrode 40 usually has a problem in adhesion to a gold bump orresistance against shock at the time of connection because the n-sideelectrode 40 undergoes the sintering treatment. However, such a problemcan be avoided in the n-side pad layer 41 in which a materialappropriate for a gold bump can be selected.

As the n-side pad layer 41, a Ti/Pt/Au laminated film is used, forexample. The thickness of this Ti/Pt/Au laminated film is 500 nm, forexample. Moreover, as described later, the n-side pad layer 41 isprovided on the laminated structure body 10 s side and can also have alayer including at least one of aluminum, an aluminum alloy, rhodium,and a rhodium alloy.

Then, an area of a region of the n-side electrode 40 in contact with then-type semiconductor layer 10 (facing region) is set smaller than anarea of a region of the highly reflective insulating layer 60 sandwichedbetween n-type semiconductor layer 10 and the n-side pad layer 41.

The area of the region of the n-side electrode 40 in contact with then-type semiconductor layer 10 (facing region) is smaller than an area ofa region of the highly reflective insulating layer 60 in contact withthe n-type semiconductor layer 10 (facing region). Simultaneously, thearea of the region of the n-side electrode 40 in contact with the n-typesemiconductor layer 10 is smaller than an area of the region of thehighly reflective insulating layer 60 in contact with the n-side padlayer 41 (facing region).

Thereby, the area of the n-side electrode 40 having a lower reflectance(area of the region where the n-side electrode 40 faces the n-typesemiconductor layer 10) is made smaller than the area of the highlyreflective insulating layer 60 having a higher reflectance (area of theregion where the highly reflective insulating layer 60 faces the n-typesemiconductor layer 10). As a result, a region that absorbs the emittinglight is reduced, and the light extraction efficiency can be improved.For example, the area of the n-side electrode 40 having good ohmicproperties and a lower reflectance is reduced to a minimum dimensionthat is necessary to reduce operating voltage. As a result, loweroperating voltage and higher light extraction efficiency can beattained.

Further, the semiconductor light emitting element 110 employs alaminated structure including the n-side electrode 40 having good ohmicproperties as an electrode connected to the n-side semiconductor 20 andthe n-side pad layer 41 having good mountability such as adhesion, forexample. Thereby, the connecting member such as a gold bump and bondingwire is connected to the n-side pad layer 41. Therefore, good connectionproperties with the connecting member such as adhesion are not demandedof the n-side electrode 40, and the n-side electrode 40 is required tosatisfy ohmic properties with respect to the n-side semiconductor layer10. For this reason, the ohmic properties with respect to n-typesemiconductor layer 10 of the n-side electrode 40 are maximized.Thereby, the area of the n-side electrode 40 can be minimized to reducethe operating voltage and obtain good operating properties.

Then, the area of the highly reflective insulating layer 60 having ahigher reflectance can be increased by the reduced area of the n-sideelectrode 40, so that the area of the highly reflective insulating layer60 can be maximized.

Then, the area of the n-side pad layer 41 can be maximized by providingthe n-side pad layer 41 not only on the n-side electrode 40 but also onthe highly reflective insulating layer 60. Then, an increased area ofthe n-side pad layer 41 facilitates formation of a gold bump, so thatthe mountability can be improved.

In other words, as described above, the area of the region of the n-sideelectrode 40 in contact with the n-type semiconductor layer 10 (facingregion) is set smaller than the area of the region of the highlyreflective insulating layer 60 in contact with the n-side pad layer 41(facing region). Thereby, the entire area of the n-side pad layer 41 canbe maximized.

Thus, according to the semiconductor light emitting element 110, thearea of the n-side electrode 40 having good ohmic properties isminimized, and the area of the highly reflective insulating layer 60 canbe maximized. Further, the area of the n-side pad layer 41 having goodmountability such as adhesion can be maximized. Consequently, asemiconductor light emitting element having low operating voltage, highlight extraction efficiency, and excellent mountability can be provided.

Namely, when the n-side electrode 40, the highly reflective insulatinglayer 60, and the n-side pad layer 41 provided thereon are disposed onthe exposed surface of the n-type semiconductor layer 10 on the firstmain surface 10 a of the semiconductor light emitting element 110, thearea of the region of the n-side electrode 40 in contact with the n-typesemiconductor layer 10 (facing region) is set smaller than the area ofthe region of the highly reflective insulating layer 60 sandwichedbetween n-type semiconductor layer 10 and the n-side pad layer 41.Thereby, the area of the region of the n-side electrode 40 directlyfacing the n-type semiconductor layer 10 can be minimized, and the areasof the highly reflective insulating layer 60 and the n-side pad layer 41can be maximized, respectively.

Further, the area of the region of the n-side electrode 40 facing then-side pad layer 41 is desirably formed smaller than the area of theregion of the highly reflective insulating layer 60 sandwiched betweenthe n-type semiconductor layer and the n-side pad layer 41. This canensure minimization of the area of the region of the n-side electrode 40directly facing the n-type semiconductor layer 10, and respectivemaximization of the areas of the highly reflective insulating layer 60and the n-side pad layer 41.

The loss caused by absorption of light in the p-side electrode 50 can besuppressed by using a material having a relatively high reflectance forthe p-side electrode 50. The configuration of the n-side electrode 40,the highly reflective insulating layer 60, and the n-side pad layer 41in this embodiment can reduce the loss caused by absorption of the lightin the n-side electrode 40.

As shown in FIG. 1B, in the semiconductor light emitting element 110,the first main surface 10 a of the laminated structure body 10 s has asquare shape, and the n-side electrode 40 is provided in a corner of thefirst main surface 10 a and close to one vertex of this square. However,the invention is not limited thereto. As describes later, variousmodifications can be made to the arrangement of the n-side electrode 40,the p-side electrode 50, the highly reflective insulating layer 60, andthe n-side pad layer 41 on the first main surface 10 a as well as thoseshapes.

Hereinafter, a specific example of the configuration of thesemiconductor light emitting element 110 and an example of themanufacturing method thereof will be described.

The laminated structure body 10 s of the semiconductor light emittingelement 110 includes a nitride semiconductor formed on the substrate 5made of sapphire, for example. Each layer that forms the laminatedstructure body 10 s is formed on the substrate 5 whose surface is formedof a sapphire c plane, for example, by using metal organic chemicalvapor deposition as follows.

Namely, first, as a buffer layer, a first AlN buffer layer having a highcarbon concentration (for example, in a carbon concentration of 3×10¹⁸cm⁻³ to 5×10²⁰ cm⁻³ and a thickness of 3 nm (nanometer) to 20 nm), asecond AlN buffer layer having high purity (for example, in a carbonconcentration of 1×10¹⁶ cm⁻³ to 3×10¹⁸ cm⁻³ and a thickness of 2 μm(micrometer)), and a non-doped GaN buffer layer (for example, thicknessof 3 μm) are sequentially formed in this order on the substrate 5. Theaforementioned first AlN buffer layer and second AlN buffer layer havinghigh purity are each a single-crystal aluminum nitride layer.

On the non-doped GaN buffer layer, as the n-type semiconductor layer 10,a Si-doped n-type GaN layer (for example, in a Si concentration of1×10¹⁸ cm⁻³ to 5×10¹⁸ cm⁻³ and a thickness of 4 μm), a Si-doped n-typeGaN contact layer (for example, in a Si concentration of 5×10¹⁸ cm⁻³ to1×10²⁰ cm⁻³ and a thickness of 0.2 μm), and a Si-doped n-typeAl_(0.10)Ga_(0.90)N clad layer (for example, in a Si concentration of1×10¹⁸ cm⁻³ and a thickness of 0.02 μm) are sequentially formed in thisorder.

On the Si-doped n-type Al_(0.11)Ga_(0.89)N clad layer, as the lightemitting layer 30, a Si-doped n-type Al_(0.11)Ga_(0.89)N barrier layerand a GaInN well layer are alternatively laminated in three periods.Further, a final Al_(0.11)Ga_(0.89)N barrier layer having a multiplequantum well structure and a Si-doped n-type Al_(0.11)Ga_(0.89)N layer(for example, in a Si concentration of 0.8×10¹⁹ cm⁻³ to 1.0×10¹⁹ cm⁻³and a thickness of 0.01 μm) are further laminated. The Si-doped n-typeAl_(0.11)Ga_(0.89)N barrier layer has a Si concentration of 1.1 ×10¹⁹cm⁻³ to 1.5×10¹⁹ cm⁻³, for example. The thickness of the finalAl_(0.11)Ga_(0.89)N barrier layer is 0.075 μm, for example. A wavelengthof the emitting light in the light emitting layer 30 is 380 m, forexample. Further, as the p-type semiconductor layer 20, a non-dopedAl_(0.11)Ga_(0.89)N spacer layer (for example, thickness of 0.02 μm), aMg-doped p-type Al_(0.28)Ga_(0.72)N clad layer (for example, in a Mgconcentration of 1×10¹⁹ cm⁻³ and a thickness of 0.02 μm), a Mg-dopedp-type GaN contact layer (for example, in a Mg concentration of 1×10¹⁹cm⁻³ and a thickness of 0.1 μm, and a heavily Mg-doped p-type GaNcontact layer (for example, in a Mg concentration 2×10²⁰ cm⁻³ and athickness of 0.02 μm) are sequentially formed in this order.

Ohmic properties with the p-side electrode 50 improve by setting the Mgconcentration of the heavily Mg-doped p-type GaN contact layer to a highvalue of not less than 1×10²⁰ cm⁻³ and less than 1×10²¹ cm⁻³. However,in the case of the semiconductor light emitting diode, unlikesemiconductor laser diodes, the heavily Mg-doped p-type GaN contactlayer is closer to the light emitting layer 30. For that reason,deterioration of properties caused by Mg diffusion is concerned. Then,using a large contact area of the p-side electrode 50 and the heavilyMg-doped p-type GaN contact layer and a low current density at the timeof operation, the Mg concentration of the heavily Mg-doped p-type GaNcontact layer is suppressed to the value not less than 1×10¹⁹ cm⁻³ andless than 1×10²⁰ cm⁻³ without significantly impairing electricalproperties. Thereby, diffusion of Mg can be prevented, and lightemitting properties can be improved.

The first AlN buffer layer having a high carbon concentration serves torelieve differences in a crystal form from that of the substrate 5 andreduces particularly screw dislocation. Moreover, a surface of thesecond MN buffer layer having high purity becomes flat at an atom level.This reduces defects of the non-doped Ga buffer layer grown on thissecond AlN buffer layer having high purity. However, in order to obtainsuch an effect, the thickness of the second AlN buffer layer having highpurity is preferably thicker than 1 μm. Moreover, in order to prevent awarp caused by distortion, the thickness of the second AlN buffer layerhaving high purity is desirably not more than 4 μm. The material usedfor the second AlN buffer layer having high purity is not limited toAlN, and Al_(x)Ga_(1-x)N (0.8≦x≦1) may be used. Thereby, a warp of wafercan be compensated.

The non-doped GaN buffer layer plays a role of reducing defects becausethe non-doped GaN buffer layer is grown by three-dimensional islandgrowth on the second AlN buffer layer having high purity. In order for agrowth surface of the non-doped GaN buffer layer to become flat, thenon-doped GaN buffer layer needs to be an average thickness of not lessthan 2 μm. From a viewpoint of repeatability and reduction in a warp, athickness of 4 μm to 10 μm is appropriate as the total thickness of thenon-doped GaN buffer layer.

By employing these buffer layers, defects can be reduced toapproximately 1/10 as compared with conventional AlN buffer layers grownat a low temperature. With this technique, in spite of heavy Si dopingof the n-type GaN contact layer and the emitting light in an ultravioletband, a highly efficiently semiconductor light emitting element can bemanufactured. Absorption of the light in the buffer layer can also besuppressed by reducing crystal defects in the buffer layer.

Thus, the laminated structure body 10 s may further include thesubstrate 5 made of sapphire and provided on a side of a second mainsurface 10 b facing the first main surface 10 a in which the n-sideelectrode 40 and the p-side electrode 50 are provided. Then, the n-typesemiconductor layer 10, the fight emitting layer 30, and the p-typesemiconductor layer 20 are desirably formed on the aforementionedsubstrate 5 via a single-crystal aluminum nitride layer (for example,the aforementioned first AlN buffer layer and second AlN buffer layerhaving high purity). The substrate 5 and at least a part of theaforementioned buffer layer may be removed also at this time.

Moreover, desirably, a portion of the aforementioned aluminum nitridelayer provided on the substrate 5 side has relatively a higherconcentration of carbon than a portion of the aforementioned aluminumnitride layer provided on a side opposite to the substrate 5. That is,the aluminum nitride layer may have a first portion and a secondportion, the first portion being provided between the substrate and asecond portion. The first portion has a carbon concentration relativelyhigher than a carbon concentration in the second portion. In otherwords, desirably, the first AlN buffer layer having a high carbonconcentration is provided on the substrate 5 side, and the second AlNbuffer layer having high purity is provided on the side opposite to thesubstrate 5.

Next, description will be given of formation of the n-side electrode 40and the p-side electrode 50 in the aforementioned laminated structurebody 10 s.

First, in a part of a region of a main surface of the laminatedstructure body 10 s, a part of the p-type semiconductor layer 20 and apart of the light emitting layer 30 are removed by dry etching using amask so that an n-type contact layer (for example, the aforementionedSi-doped n-type GaN contact layer) is exposed to the surface.

Next, a patterned resist for lift-off is formed on the exposed n-typecontact layer, and a Ti/Al/Ni/Au laminated film is formed using a vacuumevaporation apparatus to form the n-side electrode 40. The thickness ofthe Ti/Al/Ni/Au laminated film is 300 nm, for example. Then, thesintering treatment is performed in a nitrogen atmosphere at 650° C.

Next, in order to form the p-side electrode 50, a patterned resist forlift-off is formed on a p-type contact layer (for example, theaforementioned heavily Mg-doped p-type GaN contact layer). An Ag/Ptlaminated film is formed so as to have a thickness of 200 nm using avacuum evaporation apparatus. After lifting off the aforementionedresist for lift-off, the sintering treatment is performed in a nitrogenatmosphere at 650° C. Thereby, the p-side electrode 50 is formed.

Next, a dielectric laminated film serving as the highly reflectiveinsulating layer 60 is formed on the n-type semiconductor layer 10exposed from the n-side electrode 40.

In the dielectric laminated film, not less than two kinds of dielectricswhose refractive indexes are different from each other are laminated soas to form not less than two layers. For example, a laminated filmobtained by laminating five combinations of a laminated film of a firstdielectric layer (for example, a SiO₂ layer) and a second dielectriclayer (for example, a TiO₂ layer) whose refractive indexes are differentfrom each other (namely, a laminated film having a dielectric layerconsisting of ten layers in total) can be used as the dielectriclaminated film.

At this time, the thickness of the first dielectric layer and the seconddielectric layer is set at a thickness of λ/(4n) when each refractiveindex is n and a wavelength of the emitting light from the lightemitting layer 30 is λ. Namely, the dielectric laminated film is formedby alternately laminating multiple first dielectric layers having afirst refractive index n₁ and multiple second dielectric layers having asecond different refractive index n₂ different from the first refractiveindex n₁. When the wavelength of the emitting light of the lightemitting layer 30 is λ, the thickness of the first dielectric layers issubstantially λ/(4n₁), and the thickness of the second dielectric layersis substantially λ/(4n₂). Thereby, the emitting light from the lightemitting layer 30 can be reflected efficiently and can be reflected tothe first semiconductor layer 10 side and the second semiconductor layer20 side.

The highly reflective insulating layer 60 (dielectric laminated film)covers a part of the n-side electrodes 40 and may overlap the n-sideelectrode 40. Moreover, the highly reflective insulating layer 60(dielectric laminated film) does not always need to contact the n-sideelectrode 40.

Then, for example, the Ti/Pt/Au laminated film having a thickness of 500nm is formed as the n-side pad layer 41 so as to cover the n-sideelectrode 40 and the highly reflective insulating layer 60.

Next, the laminated structure body 10 s is cut by a cleavage or adiamond blade to obtain individual elements. Thus, the semiconductorlight emitting element 110 is manufactured.

A current injected from the outside of the semiconductor light emittingelement 110 into the p-side electrode 50 and flowing to the n-sideelectrode 40 through the laminated structure body 10 s is extractedthrough the n-side electrode 40 to the outside of the semiconductorlight emitting element 110. Namely, wire bonding and a bump to contactthe semiconductor light emitting element 110 with an external terminalare formed on the n-side pad layer 41. The n-side pad layer 41 isdesigned to include an area having a certain size or larger so that theaforementioned wire bonding and bump are securely disposed in a regionwithin the n-side pad layer 41. For example, the width (length) of theregion where the n-side pad layer 41 is formed is approximately 50 μm to150 μm, for example.

At this time, the area of the n-side electrode 40 having a lowreflectance can be reduced to a minimum area necessary to reduce theoperating voltage, while the area of the highly reflective insulatinglayer 60 is increased as much as possible. Additionally, the area of then-side pad layer 41 provided thereon can be increased. Thereby, theregion where the emitting light is absorbed can be reduced, thereflection region can be increased, and the light emitted from the lightemitting layer 30 can be extracted to the outside of the semiconductorlight emitting element 110 with high efficiency.

Then, the n-side pad layer 41 having adhesion and various resistancelarger than those of the n-side electrode 40 is laminated on the n-sideelectrode 40, and an external connecting member is connected to thisn-side pad layer 41. For that reason, secure electrical connection canbe obtained, and productivity can be improved. Reliability is alsoimproved.

Thus, according to the semiconductor light emitting element 110, asemiconductor light emitting element having low operating voltage, highefficiency of extracting the light, high mountability, high throughput,and high reliability can be provided.

Then, when flip chip mounting is performed, much of the emitting lightthat repeats reflection within the semiconductor layer can be reflectedto the substrate 5 side. Thereby, the light extraction efficiency can beimproved.

In the semiconductor light emitting element 110 according to thisembodiment, a material used for the semiconductor layer including then-type semiconductor layer 10, the p-type semiconductor layer 20, andthe light emitting layer 30 is not limited in particular. A galliumnitride based compound semiconductor such as Al_(x)Ga_(1-x-y)In_(y)N(x≧0, y≧0, x+y≦1) is used. A method for forming these semiconductorlayers is not limited in particular. For example, techniques such asmetal organic chemical vapor deposition and molecular beam epitaxy canbe used.

A material used for the substrate 5 is not limited in particular, andsapphire, SiC, GaN, GaAs, Si, and the like can be used. The substrate 5may be eventually removed after forming the laminated structure body 10s.

The p-side electrode 50 can include at least silver or a sliver alloy.

Reflection efficiency of a single layer film made of a metal other thansilver to light in a visible right band region is likely to deteriorateas the wavelength becomes shorter in the ultraviolet region of not morethan 400 nm. On the other hand, silver has high reflection efficiencyproperties also to the light in the ultraviolet band of not less than370 nm and not more than 400 nm. For that reason, when the semiconductorlight emitting element is one emitting ultraviolet light and the p-sideelectrode 50 is made of a silver alloy, the p-side electrode 50 on theside of the semiconductor interface desirably has a larger silvercomponent ratio. The thickness of the p-side electrode 50 is preferablynot less than 100 nm in order to ensure reflection efficiency of thelight.

The p-side electrode 50 can include a silver (Ag) contained film incontact with the p-type semiconductor layer 20 and a platinum containedfilm stacked on the silver contained film. The p-side electrode 50 isformed of the Ag/Pt laminated film, and subsequently the sinteringtreatment is performed. Thereby, Pt can be diffused very slightly at aninterface between a p-GaN contact layer (for example, the aforementionedheavily Mg-doped p-type GaN contact layer) and Ag. Thereby, adhesion ofAg improves. Additionally, contact resistance can be reduced withoutimpairing highly efficient reflectivity unique to Ag. Thereby,high-level compatibility with highly efficient reflectivity and lowoperating voltage properties, which are demanded of the p-side electrode50, can be obtained. For example, when the Ag/Pt laminated film is usedfor the p-side electrode 50, compared with a case where an Ag singlelayer film is used, the operating voltage at 20 mA can be reduced by 0.3V while an output of the light shows approximately the same value.

Ag forms a solid solution with Pt, and Ag forms a solid solution withPd. Consequently, migration of Ag can be suppressed by mixing of Pt orPd with Ag, Particularly, Pd forms a complete solid solution with Ag.Consequently, migration of Ag can be suppressed more effectively. Byusing the combination of these for the p-side electrode 50, highreliability can be obtained at the time of applying a large current.

When silver or a silver alloy is used for the p-side electrode 50, risksof inferior insulation and poor breakdown voltage caused by migration ofsilver or the silver alloy are more reduced as a distance between thep-side electrode 50 and the n-side electrode 40 is larger. The lightextraction efficiency is increased when the p-side electrode 50 facingthe n-side electrode 40 in the vicinity of a center of the semiconductorlight emitting element as viewed from a laminating direction of thelaminated structure body 10 s is formed to an edge of the p-type contactlayer as long as process conditions such as exposure precision allow.

In the semiconductor light emitting element 110, the n-side electrode 40is provided within a plane surface parallel to the first main surface 10a and closer to the p-side electrode 50 side than the highly reflectiveinsulating layer 60. Namely, in the specific example, the highlyreflective insulating layer 60 is not provided between the n-sideelectrode 40 and the p-side electrode 50. Thereby, the n-side electrode40 and the p-side electrode 50 can be laminated close to each other sothat a current can be efficiently conducted to the laminated structurebody 10 s.

When a current path that flows from the p-side electrode 50 into then-side electrode 40 is considered, the current is likely to concentrateon a region where a distance between the p-side electrode 50 and then-side electrode 40 is the shortest. Accordingly, in order to relieveelectric field concentration, it is preferably designed so that in theregion where the p-side electrode 50 contacts the n-side electrode 40,the region having the shortest distance between the p-side electrode 50and the n-side electrode 40 may be provided as long as possible.

Moreover, when viewed from the laminating direction of the laminatedstructure body 10 s, the width of the current path between the p-sideelectrode 50 and the n-side electrode 40 is wider as the distance of theregion where the p-side electrode 50 and the n-side electrode 40 faceeach other is larger. Thus, the electric field concentration is relievedto suppress deterioration of the p-side electrode 50.

In consideration of the aforementioned effect, the areas and shapes ofthe p-side electrode 50 and the n-side electrode 40 and the distancebetween the p-side electrode 50 and the n-side electrode 40 are setappropriately.

An ohmic contact region increases as the area of the n-side electrode 40is larger. As a result, the operating voltage tends to reduce. However,the current path at the time of operation tends to concentrate on then-side electrode 40 in the region where the n-side electrode 40 facesthe p-side electrode 50. For that reason, when the area of the n-sideelectrode 40 is larger than a certain size, the tendency of reduction inthe operating voltage accompanied with the increased area of the n-sideelectrode 40 is saturated. On the other hand, the smaller area of then-side electrode 40 can increase the area of the highly reflectiveinsulating layer having highly efficient reflectivity. Accordingly,improvement in the light extraction efficiency is expected. Moreover,the smaller area of the n-side electrode 40 decreases a proportion ofabsorption of the reflected light within the laminated structure body 10s when the light enters the n-side electrode 40. Accordingly,improvement in the light extraction efficiency is expected.

In consideration of the aforementioned effect, the areas and shapes ofthe n-side electrode 40 having the ohmic properties and the highlyreflective insulating layer 60 having the highly efficient reflectivityare set appropriately.

When a dielectric laminated film is used for the highly reflectiveinsulating layer 60, the reflectance increases and a margin of thethickness and wavelength also increases as a refractive index ratio ofthe combined dielectric bodies is larger and as the number ofcombinations (the number of pairs) of layers having different refractiveindexes is larger.

Moreover, the reflectance increases as an incident angle of the lightthat enters the highly reflective insulating layer 60 (for example,dielectric laminated film) from the laminated structure body 10 s isinclined with respect to a normal of the highly reflective insulatinglayer 60. Then, total reflection occurs at a certain threshold angle.

On the basis of the aforementioned properties, the conditions on thedielectric laminated film serving as the highly reflective insulatinglayer 60 are set appropriately. Thereby, the highly reflectiveinsulating layer 60 can function as a reflecting film having performancehigher than that of a metal reflection film and can improve the lightextraction efficiency. In the semiconductor light emitting element 110according to this embodiment, a design reflectance of the dielectriclaminated film used as the highly reflective insulating layer 60 is99.7%.

Oxide, nitride, acid nitride, or the like of silicon (Si), aluminum(Al), zirconium (Zr), titanium (Ti), niobium (Nb), tantalum (Ta),magnesium (Ma), hafnium (Hf), cerium (Ce), zinc (Zn), and the like canbe used for the dielectric laminated film (i.e., the highly reflectiveinsulating layer 60).

The total thickness of the laminated dielectric film is desirably notless than 50 nm for ensured insulation and desirably not more than 1000nm for suppression of cracks in the dielectric film. In order tosuppress stress between materials of different kinds caused bygeneration of heat at the time of operation, a first layer of thedielectric laminated film on the side of the semiconductor layer isparticularly preferably a material having a coefficient of linearexpansion close to that of the semiconductor layer. For example, whenthe semiconductor layer is made of GaN, the first layer of thedielectric laminated film on the side of the semiconductor layer ispreferably made of, for example, SiN. The dielectric laminated film canrelieve the stress applied to the inside of the dielectric laminatedfilm by laminating dielectric bodies of different kinds. Accordingly, ascompared with the case of a single layer, damages such as breakage,cracks, and the like are hardly generated even when the total thicknessincreases. Additionally, the dielectric laminated film can also relievethe stress applied to the semiconductor layer. Accordingly, reliabilityimproves. The effect of relieving the stress is particularly acceleratedby laminating the dielectric body having tensile stress and compressionstress.

Use of a crystal formed on a single-crystal AlN buffer layer allowsheavy Si doping of the n-type GaN contact layer to significantly reducecontact resistance with respect to the n-side electrode 40. This enablessilver or a silver alloy, which conventionally provides a highlyefficiently reflective film having poor ohmic properties and largercontact resistance, to be used as the n-side electrode 40. Furtherimprovement in the light extraction efficiency is expected. Further, byreduced crystal defects, higher light emitting efficiency can beobtained in a wavelength region shorter than 400 nm where the efficiencyusually deteriorates.

Thus, the n-side electrode 40 can include silver or a silver alloy. Inthis case, the ratio of the silver component is desirably larger on then-type semiconductor layer 10 side of the n-side electrode 40. Thethickness of the n-side electrode 40 is preferably not less than 100 nmin order to ensure the reflection efficiency to the light.

When an amorphous or polycrystalline AlN layer is provided on thesubstrate 5 in order to relieve differences in the crystal form on thesubstrate 5, the buffer layer itself acts as a light absorbing body toreduce the light extraction efficiency as a light emitting element. Toavoid this, the n-type semiconductor layer 10, the light emitting layer30, and the p-type semiconductor layer 20 are formed on the substrate 5made of sapphire via a single-crystal AlN buffer layer having a highcarbon concentration (for example, the aforementioned first AlN bufferlayer) and a single-crystal AlN buffer layer having high purity (forexample, the aforementioned second AlN buffer layer having high purity).Thereby, these buffer layers hardly absorb the light. Furthermore,thereby, crystal defects can be reduced significantly, leading tosignificant reduction in the absorber within the crystal. In this case,the number of times of reflection of the emitting light within thecrystal can be increased so that the light extraction efficiency in atransverse direction (direction toward the end face) of the laminatedstructure body 10 s can be improved. Additionally, the light can beefficiently reflected to the p-side electrode 50 and the highlyreflective insulating layer 60, which are highly efficiently reflectiveregions.

First Comparative Example

FIGS. 2A and 2B are schematic views illustrating the structure of asemiconductor light emitting element according to a first comparativeexample.

Namely, FIG. 2B is a schematic plan view, and FIG. 2A is across-sectional view taken along line A-A′ in FIG. 2B. As shown in FIG.2, in a semiconductor light emitting element 119 a according to thefirst comparative example, the n-side electrode 40 and the n-side padlayer 41 thereon are provided on the first main surface 10 a of then-type semiconductor layer 10 while the highly reflective insulatinglayer 60 is not provided.

In production of the semiconductor light emitting element 119 aaccording to the first comparative example having such a configuration,in the same manner as the semiconductor light emitting element 110, thelaminated structure body 10 s is formed, and subsequently, the p-typesemiconductor layer 20 and the light emitting layer 30 are removed so asto expose the n-type contact layer to the surface, the n-side electrode40 is formed, and the sintering treatment is performed. At this time, ashape of a mask to be used is different from that of the semiconductorlight emitting element 110, and a planar shape of the n-side electrode40 has a shape shown in FIG. 2B. Then, similarly, the p-side electrode50 is formed, and the n-side pad layer 41. is formed so as to cover then-side electrode 40.

In such a semiconductor light emitting element 119 a according to thefirst comparative example, no highly reflective insulating layer 60 isprovided; and the n-side electrode 40 having a low reflectance occupiesa large area. This causes a low extraction efficiency of the lightemitted from the light emitting layer 30.

Second Comparative Example

FIGS. 3A and 3B are schematic views illustrating the structure of asemiconductor light emitting element according to a second comparativeexample.

Namely, FIG. 3B is a schematic plan view, and FIG. 3A is across-sectional view taken along line A-A′ in FIG. 3B.

As shown in FIGS. 3A and 3B, in a semiconductor light emitting element119 b according to the second comparative example, the highly reflectiveinsulating layer 60 is provided in a region except the n-side electrode40 and the p-side electrode 50 and in the peripheral region of theelement. Then, the n-side pad layer 41 is provided on a part of thehighly reflective insulating layer 60 while covering the n-sideelectrode 40. In this case, the area of the region of the n-sideelectrode 40 in contact with the n-type semiconductor layer 10 (facingregion) is larger than the area in the region of the highly reflectiveinsulating layer 60 sandwiched by the n-type semiconductor layer 10 andthe n-side pad layer 41.

Namely, the area of the n-side electrode 40 having a low reflectance islarger than the area of the highly reflective insulating layer 60. Thiscauses a low extraction efficiency of the light in the semiconductorlight emitting element 119 b.

In the semiconductor light emitting element 119 b according to thiscomparative example, the highly reflective insulating layer 60 isprovided also in the peripheral region of the element and a regionadjacent to the p-side electrode 50. As described later, also in thesemiconductor light emitting element according to this embodiment, thehighly reflective insulating layer 60 can be provided in these regions.Accordingly, when the semiconductor light emitting element 119 baccording to the comparative example is compared with the semiconductorlight emitting element 110, comparison is only made about the region ofthe n-side electrode 40. In this comparison, the semiconductor lightemitting element 119 b according to this comparative example has thelight extraction efficiency relatively lower than that of thesemiconductor light emitting element 110.

Third Comparative Example

FIGS. 4A and 4B are schematic views illustrating the structure of asemiconductor light emitting element according to a third comparativeexample.

Namely, FIG. 4B is a schematic plan view, and FIG. 4A is across-sectional view taken along line A-A′ in FIG. 4B.

As shown in FIGS. 4A and 4B, a semiconductor light emitting element 119c according to the third comparative example has an increased region ofthe highly reflective insulating layer 60 in the vicinity of the n-sideelectrode 40 compared with the semiconductor light emitting element 119b according to the second comparative example. Accordingly, the area ofthe region of the n-side electrode 40 in contact with the n-typesemiconductor layer 10 (facing region) is smaller than the area of theregion of the highly reflective insulating layer 60 in contact with then-type semiconductor layer 10 (facing region). However, in this case,the n-side pad layer 41 is provided only on the n-side electrode 40, andthe n-side pad layer 41 is not provided on the highly reflectiveinsulating layer 60.

The semiconductor light emitting element 119 c according to thiscomparative example having such a configuration has a reduced area inwhich the n-side electrode 40 having a low reflectance contacts then-type semiconductor layer 10 and an increased area of the highlyreflective insulating layer 60. This causes high light extractionefficiency. On the other hand, the n-side pad layer 41 is not providedon the highly reflective insulating layer 60, and the area of the n-sidepad layer 41 is small. This causes poor mountability, resulting indifficulties in miniaturization of the element, a reduced yield, anddeteriorated productivity, for example. Moreover, the material used forthe n-side electrode 40 and the sintering conditions need to satisfygood ohmic properties with the n-type semiconductor layer 10, adhesionto the highly reflective insulating layer 60, and no diffusion of a partof the material of the highly reflective insulating layer 60 to then-side electrode 40 even when sintering is performed on the n-sideelectrode 40 contacting the highly reflective insulating layer 60.Accordingly, severe restrictions are imposed on the material used forthe n-side electrode 40 and the sintering conditions. As a result, then-side electrode 40 cannot obtain sufficient high ohmic properties withthe n-type semiconductor layer 10. When the area of the n-side electrode40 is increased in order to reduce the operating voltage, the lightextraction efficiency deteriorates.

Fourth Comparative Example

FIGS. 5A and 5B are schematic views illustrating the structure of asemiconductor light emitting element according to a fourth comparativeexample.

Namely, FIG. 5B is a schematic plan view, and FIG. 5A is across-sectional view taken along line A-A′ in FIG. 5B.

As shown in FIGS. 5A and 5B, a semiconductor light emitting element 119d according to the fourth comparative example does not have the n-sidepad layer 41 in the semiconductor light emitting element 119 c accordingto the third comparative example. The structure of the first mainsurface 10 a of the semiconductor light emitting element 119 d issimilar to that disclosed in JP-A 2007-324585 (Kokai).

The semiconductor light emitting element 119 d according to thecomparative example having such a configuration has a reduced area inwhich the n-side electrode 40 having a low reflectance contacts then-type semiconductor layer 10 and an increased area of the highlyreflective insulating layer 60. This causes high light extractionefficiency. However, the n-side pad layer 41 is not provided on then-side electrode 40, and the connecting member such as a gold bump andbonding wire contacts the n-side electrode 40 directly.

Accordingly, the material used for the n-side electrode 40 and thesintering conditions need to satisfy good ohmic properties with then-type semiconductor layer 10, adhesion to the connecting member such asa gold bump and bonding wire, resistance against diffusion of variouselements included in the connecting member, and resistance againstincrease in a temperature during a process to mount the connectingmember. For this demand, severe restrictions are imposed on the materialused for the n-side electrode 40 and the sintering conditions to narrowa selection range of the material and the sintering conditions. As aresult, the n-side electrode 40 cannot obtain sufficiently high ohmicproperties with the n-type semiconductor layer 10. Thus, in thesemiconductor light emitting element 119 d according to the comparativeexample, the operating voltage increases when reliability issufficiently secured. The light extraction efficiency deteriorates whenthe area of the n-side electrode 40 is increased.

On the other hand, as already described, in the semiconductor lightemitting element 110 according to this embodiment, use of the laminationlayer structure formed of the n-side electrode 40 and the n-side padlayer 41 relieves the demand for the material used for the n-sideelectrode 40 so that a material having good ohmic properties can beused. In addition, the area of the n-side electrode 40 can be reduced toa necessary minimum, the area of the highly reflective insulating layer60 is increased as large as possible, and the area of the n-side padlayer 41 provided thereon can be increased. Thereby, it is possible toprovide the semiconductor light emitting element having enhancedmountability, reduced operating voltage, and high light extractionefficiency while sufficiently ensuring reliability.

FIGS. 6A and 6B are schematic views illustrating the configuration ofanother semiconductor light emitting element according to the firstembodiment of this invention.

Namely, FIG. 6B is a schematic plan view, and FIG. 6A is across-sectional view taken along line A-A′ in FIG. 6B.

As shown in FIGS. 6A and 6B, in another semiconductor light emittingelement 111 according to this embodiment, the n-side electrode 40includes a transparent conductive film 42. In this specific example, then-side electrode 40 has the transparent conductive film 42 and areflective metal film 43. Except this, portions can be the same as thoseof the semiconductor light emitting element 110, and description thereofwill be omitted.

The transparent conductive film 42 is provided in contact with then-type semiconductor layer 10. The reflective metal film 43 is providedon the transparent conductive film 42 on a side opposite to the n-typesemiconductor layer 10. Namely, for example, the reflective metal film43 is provided between the transparent conductive film 42 and the n-sidepad layer 41.

The transparent conductive film 42 has translucency to the light emittedfrom the light emitting layer 30. A material having good ohmicproperties with the n-type semiconductor layer can be used for thetransparent conductive film 42.

On the other hand, the reflective metal film 43 can be provided so asnot to contact the n-type semiconductor layer 10. Accordingly, thereflective metal film 43 may just satisfy a property of a highreflectance as long as conduction of current between the n-side padlayer 41 and the transparent conductive film 42 is possible.

Thus, the n-side electrode 40 in the semiconductor light emittingelement 111 is provided on the n-type semiconductor layer 10 side andincludes the transparent conductive film 42 having translucency to thelight emitted from the light emitting layer 30.

A film made of a material having a band gap larger than the wavelengthof the emitting light transmitted can be used for the transparentconductive film 42. Alternatively, a metal film whose thickness issufficiently thinner than that determined by the inverse number of anabsorption coefficient in the wavelength of the emitting lighttransmitted can be used. A transparent conductive layer including atleast one of nickel, indium tin oxide, and zinc oxide, for example, canbe used for the transparent conductive film 42.

The reflective metal film 43 includes at least a metal film having highreflection properties to the emitting light. Silver or aluminum, whichis a metal showing high reflectivity to the emitting light at 370 to 400nm, can be used as the reflective metal film 43.

The entire reflective metal film 43 can be covered with the n-side padlayer 41, allowing a configuration in which a gold bump and the like areformed so as not to contact the reflective metal film 43. Accordingly,adhesion demanded of the reflective metal film 43 is more relieved thanthat demanded of the p-side electrode 40 and the n-side pad layer 41.

The transparent conductive film 42 has the following roles: a role oftransmitting the light from the light emitting layer 30 reflected withinthe semiconductor light emitting element 111 to reflect the light by thereflective metal film 43; a role of contacting the n-type semiconductorlayer 10 with good electrical properties; and a role of preventing areaction of silver or aluminum used in the reflective metal film 43 withthe n-type semiconductor layer 10 or diffusion of silver or aluminumwithin the n-type semiconductor layer 10. For this reason, preferably,the planar shape of the transparent conductive film 42 is substantiallythe same as the planar shape of the reflective metal film 43.

The thickness of the transparent conductive film 42 is arbitrary and isbetween 1 nm to 500 nm, for example.

According to the semiconductor light emitting element 111 having such aconfiguration, a transparent conductive film 42 having good ohmicproperties is disposed on the n-type semiconductor layer 10 side of then-side electrode 40, and the reflective metal film 43 havingconductivity and reflectivity is disposed on the transparent conductivefilm 42. This allows compatibility of high ohmic properties and highreflectance and also can improve reliability.

The n-side electrode 40 may not have the reflective metal film 43, andthe entire n-side electrode 40 may be the transparent conductive film42. Namely, the n-side electrode 40 may be a transparent conductive filmthat includes at least one of nickel, indium tin oxide, and zinc oxide,electrically contacts the n-type semiconductor layer 10 and the n-sidepad layer 41, and has translucency to the light emitted from the lightemitting layer 30. In this case, the light that passes through then-side electrode 40 is reflected by the n-side pad layer 41, advances tothe laminated structure body 10 s side, and is extracted to the outside.

FIGS. 7A and 7B are schematic views illustrating the configuration ofanother semiconductor light emitting element according to the firstembodiment of this invention.

Namely, FIG. 7B is a schematic plan view, and FIG. 7A is across-sectional view taken along line A-A′ in FIG. 7B.

As shown in FIGS. 7A and 7B, in a semiconductor light emitting element112 according to this embodiment, the n-type semiconductor layer 10 andthe p-type semiconductor layer 20 on the first main surface 10 a of thelaminated structure body 10 s are covered with the highly reflectiveinsulating layer 60 (for example, a dielectric laminated film) except apart of an opening. A diffusion prevention layer 53 is provided on thep-side electrode 50, and a p-side pad layer 51 is provided thereon. Thep-type semiconductor layer 20 and the light emitting layer 30 on thefirst main surface 10 a of the laminated structure body 10 s have a mesaportion having a sloped tapered portion. Except this, portions can bethe same as those of the semiconductor light emitting element 110, anddescription thereof will be omitted.

Such a semiconductor light emitting element 112 is manufactured, forexample, as follows. Namely, similarly to the semiconductor lightemitting element 110, the laminated structure body 10 s is formed, andsubsequently, the p-type semiconductor layer 20 and the light emittinglayer 30 are removed so as to expose the n-type contact layer to thesurface. The etching treatment at this time is performed so that themesa portion of the laminated structure body 10 s has a tapered shapewhose inclination from the normal of the first main surface 10 a isapproximately 70 degrees, for example.

Subsequently, using a thermal CVD system, a SiO₂ film serving as adielectric film is formed in a thickness of 200 nm on the first mainsurface 10 a of the laminated structure body 10 s.

Next, a patterned resist for lift-off is formed on an n-type contactlayer (for example, the aforementioned Si-doped n-type GaN contactlayer), and a part of the SiO₂ film on the exposed n-type contact layeris removed by ammonium hydrogen fluoride treatment, for example. Using avacuum evaporation apparatus, a Ti/Al/Ni/Au laminated film serving asthe n-side electrode 40 having a thickness of 300 nm, for example, isformed in the region from which the SiO₂ film is removed. After liftingoff the resist for lift-off, the sintering treatment is performed undera nitrogen atmosphere at 650° C. Thereby, the n-side electrode 40 isformed. The width of the n-side electrode 40 is 10 μm.

Next, in order to form the p-side electrode 50, a patterned resist forlift-off is formed on a p-type contact layer (for example, theaforementioned heavily Mg-doped p-type GaN contact layer), and ammoniumhydrogen fluoride treatment is performed to expose the p type contactlayer. At that time, a time of the ammonium hydrogen fluoride treatmentis adjusted so that the p type contact layer may be exposed between thep-side electrode 50 and the SiO₂ film of a dielectric film.Specifically, the total time of a time for removing the SiO₂ film in theregion where the p-side electrode 50 is formed and a time of overetching to expose the p type contact layer located immediately next tothe aforementioned region in width of 1 μm is approximately 3 minutes atan etching rate of 400 nm/min., for example. Using a vacuum evaporationapparatus, an Ag/Pt laminated film having a thickness of 200 nm, forexample, is formed in the region from which the SiO₂ film is removed.After lifting off, a sintering treatment is performed under an oxygenatmosphere at 350° C.

Next, by a lift-off method, five combinations of a Pt film and a W filmare formed as the diffusion prevention layer 53 so as to cover thep-side electrode 50. The total thickness of the diffusion preventionlayer 53 is 600 nm, for example.

Next, a dielectric laminated film serving as the highly reflectiveinsulating layer 60 is formed on the p type semiconductor layer 20 wherethe p-side electrode 50 is not formed, and on the dielectric film of then-type semiconductor layer 10. For example, five combinations of a SiO₂film and a TiO₂ film are laminated. However, the dielectric laminatedfilm may be removed in the periphery of the element, or the dielectriclaminated film may be damaged by an isolation process or the like in theperiphery of the element.

In FIGS. 7A and 7B, although the highly reflective insulating layer 60does not contact the p-side electrode 50 and the n-side electrode 40, apart of the highly reflective insulating layer 60 may overlap the top ofthe p-side electrode 50 or the n-side electrode 40.

Then, a Ti/Pt/Au laminated film serving as the n-side pad layer 41 andthe p-side pad layer 51 is formed so as to cover a part of the highlyreflective insulating layer 60 while covering the p-side electrode 50and the n-side electrode 40. The lift-off method is used for thisformation, for example. The thickness of the highly reflectiveinsulating layer 60 is 1000 nm, for example.

Then, the laminated structure body 10 s is cut by a cleavage or adiamond blade to separate individual elements. Thus, the semiconductorlight emitting element 112 is manufactured. The size of thesemiconductor light emitting element 112 is a square of 300 μm inlength, for example.

In the aforementioned process, before the p-side electrode 50 and then-side electrode 40 as an ohmic metal are formed, the dielectric film(the above-mentioned SiO₂ film) is formed in the semiconductor layer ofthe laminated structure body 10 s. Thereby, contamination that adheresto an interface between the electrode and the semiconductor layer in anelectrode formation process can be significantly reduced, thereforeallowing improvement in reliability, a yield, electrical properties, andoptical properties.

When the n-side electrode 40 has a low reflectance and the regionexcluding the n-side electrode 40 and including the p-side electrode 50has a high reflectance, it is desirable that the distance between thep-side electrode 50 and the n-side electrode 40 is formed slightlylarger because the light emitted directly under the p-side electrode 50facing the n-side electrode 40 is reflected by an interface between thesubstrate 5 made of sapphire and the crystal layer and immediatelyreaches to the n-side electrode 40 to be absorbed.

For example, when the width of the n-side electrode 40 is 10 μm, theproportion of the area of the n-side electrode 40 on an electrodeformation surface (the first main surface 10 a) of the semiconductorlight emitting element 112 is approximately 13% in the semiconductorlight emitting element 119 a according to the first comparative example.On the other hand, the proportion of the area of the n-side electrode 40is approximately 2% in the semiconductor light emitting element 112according to this specific example, and the proportion of the area ofthe n-side electrode 40 can be significantly reduced. Thus, according tothe semiconductor light emitting element 112, the light absorbing regioncan be significantly reduced. In addition, by forming the highlyreflective insulating layer 60 in the reduced absorbing area, thereflection region can be increased to further improve the lightextraction efficiency.

The p-side electrode 50 is covered with the diffusion prevention layer53 and the p-side pad layer 51 to be isolated from open air.Accordingly, the p-side electrode 50 is hard to be exposed to moistureor ion impurities so that migration, oxidization, sulfuration reactionin the p-side electrode 50 can be suppressed.

Moreover, the p-side pad layer 51 is formed closely contacting the endof the p-side electrode 50 on the side in which the p-side electrode 50and the n-side electrode 40 face each other. The current path is formedclosely contacting the p-side electrode 50 to relieve currentconcentration on the p-side electrode 50.

Simultaneously, a region sandwiched by the p-type semiconductor layer 20and the p-side pad layer 51 is formed in the vicinity of the end of theregion where the p-side electrode 50 faces the dielectric film (theaforementioned SiO₂ film) and in the vicinity the end of the regionwhere the p-side electrode 50 faces the highly reflective insulatinglayer 60, respectively. Accordingly, a weak electric field is appliedbetween the p-type semiconductor layer 20 and the p-side pad layer 51through the dielectric film or the highly reflective insulating layer60. As a result, a structure where the electric field becomes graduallyweak from the p-side electrode 50 to the dielectric film or the highlyreflective insulating layer 60 can be provided to relieve the electricfield concentration on this region.

The semiconductor light emitting element according to this embodimentneeds no special device in the manufacturing process and can be formedwith the same process and the number of the process as those in thepast. These effects can bring reduced leakage current, improvedinsulating properties, improved breakdown voltage properties, improvedluminescence intensity, increased life span, high throughput, and lowcost of the semiconductor light emitting element.

When the length of which the p-side pad layer 51 covers the dielectricfilm or the highly reflective insulating layer 60 is long, it isadvantage in obtaining the structure to relieve the electric field viathe dielectric film or the highly reflective insulating layer 60.However, a risk of a short of the p-side electrode 50 and the n-sideelectrode 40 is increased. On the other hand, when the length is short,the risk of a short of the p-side electrode 50 and the n-side electrode40 is decreased.

The reflection region can be significantly increased by forming thehighly reflective insulating layer 60 in approximately all the region ofthe first main surface 10 a in which the p-side electrode 50 and then-side electrode 40 are not formed. This can improve the lightextraction efficiency.

The tapered shape can prevent disconnection of the dielectric film andthe highly reflective insulating layer 60 when the n-type semiconductorlayer 10 is exposed.

The highly reflective insulating layer 60 formed on the tapered slopedsurfaces has a thickness thinner than that of the highly reflectiveinsulating layer 60 formed on a parallel surface (the surface parallelto the first main surface 10 a). Accordingly, when the thickness of eachlayer to the emitting light is optically designed on the parallelsurface, the conditions on the tapered sloped surface are deviated fromthe optical design so that reflectivity in the region deteriorates. Bymaking the taper angle small (making an angle between the first mainsurface 10 a and the sloped surface small), the thickness of each filmincluded in the highly reflective insulating layer 60 formed on thesloped surfaces approaches the thickness of the flat surface. Then,reflectivity close to that of the optical design is obtained also on thesloped surfaces. From a viewpoint of the light extraction efficiency, anoptimal taper angle varies depending on the shape of the semiconductorlight emitting element or the shape of the p-side electrode 50. Thetaper angle can be determined in consideration of these.

The diffusion prevention layer 53 provided between the p-side electrode40 and the p-side pad layer 51 suppresses substances included in thep-side pad layer 51 from being diffused toward the p-side electrode 50or the substances from reacting with a material included in the p-sideelectrode 50. For this purpose, a material that does not react withsilver used for the p-side electrode 50 or is not actively diffused tosilver can be used for the diffusion prevention layer 53. A single layerfilm or a laminated film including high melting point metals, such asvanadium (V), chromium (Cr), iron (Fe), cobalt (Co), nickel (Ni),niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), tantalum(Ta), tungsten (W), rhenium (Re), iridium (Ir), platinum (Pt), forexample, can be used for the diffusion prevention layer 53.

More desirably, to avoid problems even if some are diffused, iron (Fe),cobalt (Co), nickel (Ni), rhodium (Rh), tungsten (W), rhenium (Re),iridium (Ir), and platinum (Pt) are used for the diffusion preventionlayer 53 as a metal having high work function and being easy to provideohmic properties with the p-GaN contact layer (for example, theaforementioned heavily Mg-doped p-type GaN contact layer),

In the case of a single layer film, the thickness of the diffusionprevention layer 53 is desirably 5 nm to 200 nm so that a film state maybe maintained. In the case of a laminated film, the thickness is notlimited in particular, and can be selected between 10 nm and 10000 nm,for example.

Next, a variation of the semiconductor light emitting element accordingto this embodiment will be described.

FIGS. 8A to 8D are schematic plan views illustrating the configurationsof other semiconductor light emitting elements according to the firstembodiment of this invention.

Namely, FIGS. 8A to 8D show the configurations of other semiconductorlight emitting elements 113 to 116 according to this embodiment and areschematic plan views when viewed from the laminating direction of thelaminated structure body 10 s of the semiconductor light emittingelement.

In these semiconductor light emitting elements 113 to 116, the n-sideelectrode 40 is disposed not in a corner of the first main surface 10 aof the laminated structure body 10 s but in the central portion of aside of the first main surface 10 a. In this case as well, the area ofthe region of the n-side electrode 40 in contact with the n-typesemiconductor layer 10 (facing region) is smaller than the area of theregion of the highly reflective insulating layer 60 sandwiched betweenthe n-type semiconductor layer 10 and the n-side pad layer 41. Thereby,in the semiconductor light emitting elements 113 to 116 as well, asemiconductor light emitting element having low operating voltage, highlight extraction efficiency, high mountability, high throughput, andhigh reliability can be provided.

As shown in FIG. 8A, in the semiconductor light emitting element 113,the p-side electrode 50 has a planar shape with a recess. This recess isprovided in the central portion of the first main surface 10 a. Then-side electrode 40 has a first side part 40 p 1 along one side of thefirst main surface 10 a of the laminated structure body 10 s, a secondside part 40 p 2, and a third side part 40 p 3 between the first sidepart 40 p 1 and the second side part 40 p 2. The n-side electrode 40also has a central extended part 40 p 4 along the recess of the p-sideelectrode 50 and a central part 40 p 5 that connects the first side part40 p 1, the second side part 40 p 2, and the central extended part 40 p4.

Then, the highly reflective insulating layer 60 is provided in a regionsurrounded by the third side part 40 p 3 and the central part 40 p 5.

The n-side pad layer 41 is provided so as to cover the first side part40 p 1, the second side part 40 p 2, the third side part 40 p 3, centralextended part 40 p 4 and the central portion 40 p 5 of the n-sideelectrode 40 and the highly reflective insulating layer 60. A gold bumpor a bonding wire is provided on the n-side pad layer 41 in a region onthe highly

In the semiconductor light emitting element 113 as well, the n-sideelectrode 40 is provided in a portion facing the p-side electrode 50 inthe n-type semiconductor layer 10. Thereby, electrical properties can beimproved effectively to reduce the operating voltage.

As shown in FIG. 8B, in the semiconductor light emitting element 114,the third side part 40 p 3 in the configuration of the semiconductorlight emitting element 113 is omitted, and the highly reflectiveinsulating layer 60 is provided in the region. A portion that does notface the p-side electrode 50 in the n-side electrode 40 contributeslittle to electrical conduction of current and exerts little influenceon the electrical properties. Accordingly, even if the third side part40 p 3 is not provided, the electrical properties hardly change. Then,omission of the third side part 40 p 3 can further increase the area ofthe highly reflective insulating layer 60 and can further increase theregion having a high reflectance so that the light extraction efficiencyfurther improves.

As shown in FIG. 8C, in the semiconductor light emitting element 115,the central part 40 p 5 in the configuration of the semiconductor lightemitting element 114 is also omitted, and the n-side electrode 40 hasthe first side part 40 p 1, the second side part 40 p 2, and the centralextended part 40 p 4. The first side part 40 p 1, the second side part40 p 2, and the central extended part 40 p 4 are covered with the n-sidepad layer 41, thereby to connect the first side part 40 p 1, the secondside part 40 p 2, and the central extended part 40 p 4 to each other,The first side part 40 p 1, the second side part 40 p 2, and the centralextended part 40 p 4 are also electrically connected to a gold bump anda bonding wire via the n-side pad layer 41.

In the semiconductor light emitting element 115, omission of the thirdside part 40 p 3 and the central portion 40 p 5 can further increase thearea of the highly reflective insulating layer 60 and can furtherincrease the region having a high reflectance so that the lightextraction efficiency further improves. The light extraction efficiencycan be Improved without changing the electrical properties much byappropriately designing the lengths of portions of the first side part40 p 1, the second side part 40 p 2, and the central extended part 40 p4 facing the p-side electrode 50.

As shown in FIG. 8D, in the semiconductor light emitting element 116 aswell, the n-side electrode 40 has the first side part 40 p 1, the secondside part 40 p 2, and the central extended part 40 p 4. The highlyreflective insulating layer 60 is provided on the n-type semiconductorlayer 10 of a region in which the first side part 40 p 1, the secondside part 40 p 2, and the central extended part 40 p 4 are not provided.The n-side pad layer 41 is provided on the highly reflective insulatinglayer 60. Then, each part of the first side part 40 p 1, the second sidepart 40 p 2 and the central extended part 40 p 4, and the highlyreflective insulating layer 60 are covered with the n-side pad layer 41.In other words, in this specific example, each part of the first sidepart 40 p 1, the second side part 40 p 2 and the central extended part40 p 4 are not covered with the n-side pad layer 41.

In this case as well, omission of the third side part 40 p 3 and thecentral portion 40 p 5 can further increase the area of the highlyreflective insulating layer 60 and can further increase the regionhaving a high reflectance so that the light extraction efficiencyfurther improves.

In the semiconductor light emitting element 116 according to thespecific example, the n-side electrode 40 not covered with the n-typepad layer 41 is preferably covered with the highly reflective insulatinglayer 60 from a viewpoint of reliability and a mounting process.Thereby, a design margin of the periphery of the n-side electrode 40 isincreased. As a result, improvement in the light extraction efficiencyby increasing the area of the p-side electrode 40 and improvement inthroughput by increasing a margin of alignment accuracy at the time offorming the n-side electrode 40 can be expected.

In the semiconductor light emitting device according to this embodiment,the region in which the n-side pad layer 41 is provided has a shapewhose length and width are relatively close to each other, such as asquare or a rectangular or ellipse form relatively closer to a circle,as in the semiconductor light emitting devices 111 to 116. A ratio ofthe peripheral length to the area of the n-side pad layer 41 isrelatively small. On the other hand, in order to effectively feedcurrent in the portion facing the p-side electrode 50, the n-sideelectrode 40 has a shape aligned with the edges of the p-side electrode50, and a ratio of a peripheral length to the area of the n-sideelectrode 40 is relatively large. Thus, the planar shape of the n-sidepad layer 41 has a block shape, and the planar shape of the n-sideelectrode 40 has a shape having branches extended from the block.

FIG. 9 is a schematic cross-sectional view illustrating theconfiguration of another semiconductor light emitting element accordingto the first embodiment of this invention.

As shown in FIG. 9, in a semiconductor light emitting element 117according to this embodiment, the n-side pad layer 41 has a plurality oflayers of a first n-side pad layer 411 and a second n-side pad layer 412laminated on the first n-side pad layer 411. Except this, portions canbe the same as those in the semiconductor light emitting element 110,and description thereof will be omitted.

The first n-side pad layer 411 is provided on the side of the n-sideelectrode 40 and the highly reflective insulating layer 60. The firstn-side pad layer 411 may have reflectance to the emitting light higherthan that of the second n-side pad layer 412. A material used for thefirst pad layer 411 is selected by placing importance on at least one ofreflectance and adhesion to the highly reflective insulating layer 60.For example, Ag and Al can be used for the first pad layer 411.Furthermore, a heat treatment may be performed to improve adhesionbetween the first n-side pad layer 411 and the highly reflectiveinsulating layer 60.

On the other hand, a material used for the second pad layer 412 isselected by placing importance on adhesion to the connecting member suchas a gold bump and a bonding wire, resistance against diffusion ofvarious elements included in the connecting member, resistance againstincrease in a temperature during the mounting process to the connectingmember, and the like. For example, Au is used for the second pad layer412.

The n-type pad layer 41 has such a laminated layer structure of thefirst n-side pad layer 411 and the second n-side pad layer 412 so thatperformance demanded of the lower part and that demanded of the upperpart of the n-side pad layer 41 can be separated, and the highestperformance can be demonstrated. Thereby, the mountability, theoperating properties, and the light extraction efficiency can be furtherimproved.

The configuration in which the n-side pad layer 41 has the laminatedlayer structure can also be applied to all of the semiconductor lightemitting elements according to the already described embodiments of thisinvention, and the same effect can be obtained.

Second Embodiment

A semiconductor light emitting device of this invention is asemiconductor light emitting device using a semiconductor light emittingelement according to the first embodiment. Here, while any of thesemiconductor light emitting elements according to the first embodimentcan be used for this semiconductor light emitting element, an exampleusing the semiconductor light emitting element 110 will be describedbelow.

FIG. 10 is a schematic cross-sectional view illustrating theconfiguration of a semiconductor light emitting device according to asecond embodiment of this invention.

As shown in FIG. 10, a semiconductor light emitting device 201 accordingto this embodiment includes the semiconductor light emitting element 110and a submount 24 (mounting component) on which the semiconductor lightemitting element 110 is mounted.

The submount 24 has a plurality of mounting electrodes. In the specificexample, the submount 24 has an n-side mounting electrode 24 a (firstmounting electrode) and a p-side mounting electrode 24 b (secondmounting electrode).

The first main surface 10 a of the semiconductor light emitting element110 is disposed facing the submount 24. The n-side pad layer 41 iselectrically connected to one of the mounting electrodes of the submount24, and the p-side electrode 50 is electrically connected to the otherof the mounting electrodes of the submount 24. Namely, for example, then-side pad layer 41 is electrically connected to the n-side mountingelectrode 24 a, and the p-side electrode 50 is electrically connected tothe p-side mounting electrode 24 b.

In other words, the semiconductor light emitting device 201 has aconfiguration in which the semiconductor light emitting element 110 ismounted by a flip chip method.

The semiconductor light emitting device further includes a wavelengthconversion layer 210 that absorbs the light emitted from the lightemitting layer 30 of the semiconductor light emitting element 110 (firstlight) and emits light (second light) having a wavelength different fromthat of the light (the first light). A first fluorescent layer 211 and asecond fluorescent layer 212 described later, for example, can be usedfor the wavelength conversion layer 210.

According to the semiconductor light emitting device 201 having such aconfiguration, use of the semiconductor light emitting element accordingto the embodiments of this invention can provide a flip chip typesemiconductor light emitting device having high mountability, goodoperating properties (low operating voltage), and high light extractionefficiency. Additionally, providing the aforementioned wavelengthconversion layer 210 can provide a light emitting device having desiredcolor properties.

Hereinafter, a specific example of the semiconductor light emittingdevice 201 will be further described.

As shown in FIG. 10, in the semiconductor light emitting device 201according to this embodiment, a reflecting film 23 is provided on aninner surface of a container 22 made of ceramics or the like. Thereflecting film 23 is separately provided on the inner side surfaces andthe bottom surface of the container 22. The reflecting film 23 is madeof aluminum, for example. Among these, the semiconductor light emittingelement 110 shown in FIG. 1 is installed on the reflecting film 23provided on the bottom surface of the container 22 via the submount 24.

A first gold bump 25 a and a second gold bump 25 b are provided on then-side pad layer 41 and the p-side electrode 50 (or p-side pad layer 51)of the semiconductor light emitting element 110, respectively, by a ballbonder. Thereby, the semiconductor light emitting element 110 is fixedonto the submount 24.

Namely, the n-side mounting electrode 24 a and the p-side mountingelectrode 24 b insulated from each other are provided on the surface ofthe submount 24. The n-side pad layer 41 is electrically connected tothe n-side mounting electrode 24 a, the p-side electrode 50 iselectrically connected to the p-side mounting electrode 24 b, and thesemiconductor light emitting element 110 is fixed onto the submount 24.The semiconductor light emitting element 110 may be directly fixed ontothe submount 24 without using the first and second gold bumps 25 a and25 b.

These semiconductor light emitting element 110, submount 24, andreflecting film 23 can be fixed using adhesion by an adhesive, solder,and the like.

The n-side mounting electrode 24 a and the p-side mounting electrode 24b of the submount 24 are respectively connected by a bonding wire 26 toan electrode provided on the container 22 side, which is not shown. Thisconnection is made in a portion between the reflecting film 23 on theinner side surfaces and the reflecting film 23 on the bottom surface.

A first fluorescent layer 211 including a red fluorescent body isprovided so as to cover the semiconductor light emitting element 110 andthe bonding wire 26. On this first fluorescent layer 211, a secondfluorescent layer 212 including blue, green, or yellow fluorescent bodyis provided. On these fluorescent layers, a cover 27 made of a siliconeresin is provided.

The first phosphor layer 211 includes a resin and a red fluorescent bodydispersed in this resin.

As the red fluorescent body, for example, Y₂O₃, YVO₄, and Y₂(P, V)O₄ canbe used as a base material, and trivalent Eu (Eu³⁺) is included in thisbase material as an activation substance. Namely, Y₂O₃:Eu³⁺, YVO₄:Eu³⁺,and the like can be used as the red fluorescent body. The concentrationof Eu3+ can be 1% to 10% in a mol concentration. As the base materialfor the red fluorescent body, LaOS and Y₂(P, V)O₄ can be used besidesY₂O₃ and YVO₄. Mn⁴⁺ and the like can also be used besides Eu³⁺.Particularly, absorption of the light at 380 nm increases by adding asmall amount of Bi with trivalent Eu to the base material of YVO₄,resulting in further increased light emitting efficiency. As the resin,a silicone resin and the like can be used, for example.

The second fluorescent layer 212 includes the resin and at least one ofthe fluorescent bodies of blue, green and yellow dispersed in thisresin. For example, a fluorescent body in combination with the bluefluorescent body and the green fluorescent body may be used, afluorescent body in combination with the blue fluorescent body and theyellow fluorescent body may be used, or a fluorescent body incombination with the blue fluorescent body, the green fluorescent body,and the yellow fluorescent body may be used.

As the blue fluorescent body, (Sr, Ca)₁₀(PO₄)₆Cl₂:Eu²⁺,BaMg₂Al₁₆O₂₇:Eu²⁺, and the like can be used, for example.

As the green fluorescent body, Y₂SiO₅:Ce³⁺ and Tb³⁺ in which trivalentTb is an emission center can be used, for example. In this case,excitation efficiency improves by transmitting energy to Tb ions from Ceions. As the green fluorescent body, Sr₄Al₁₄O₂₅:Eu²⁺ and the like can beused, for example.

As the yellow fluorescent body, Y₃Al₅:Ce³⁺ and the like can be used, forexample.

A silicone resin and the like can be used as the resin, for example.

Particularly, trivalent Tb has sharp light emission in the vicinity of550 nm where luminosity factor is at the maximum, and a combination oftrivalent Tb with trivalent Eu having sharp red light remarkablyimproves light emitting efficiency.

According to the semiconductor light emitting device 201 according tothis embodiment, 380 nm ultraviolet light generated from thesemiconductor light emitting element 110 is emitted to the substrate 5side of the semiconductor light emitting element 110. The aforementionedfluorescent bodies included in each of the fluorescent layers can beefficiently excited by using also reflection in the reflecting film 23.

For example, the aforementioned fluorescent body having trivalent Eu orthe like included in the first fluorescent layer 211 as an emissioncenter can be converted into light having a narrow wavelengthdistribution in the vicinity of 620 nm to efficiently obtain red visiblelight.

The blue, green, and yellow fluorescent bodies included in the secondfluorescent layer 212 can be also efficiently excited to obtain visiblelight of blue, green, and yellow efficiently.

As these mixed colors, white light and light of other various colors canbe obtained with a high efficient ratio and good color renderingproperties.

Next, a method for manufacturing the semiconductor light emitting device201 according to this embodiment will be described.

The already described method can be used as a process of manufacturingthe semiconductor light emitting element 110. Accordingly, a processafter the semiconductor light emitting element 110 is completed will bedescribed below.

First, a metal film serving as the reflecting film 23 is formed on theinner surface of the container 22 by, for example, a spattering method.This metal film is patterned so that the reflecting film 23 is left onthe inner side surfaces and the bottom surface of the container 22,respectively.

Next, the first and second gold bumps 25 a and 25 b are disposed by aball bonder in the semiconductor light emitting element 110. Thesemiconductor light emitting element 110 is fixed onto the submount 24having the n-side mounting electrode 24 a and the p-side mountingelectrode 24 b. This submount 24 is installed and fixed on thereflecting film 23 of the bottom surface of the container 22. Thesecomponents can be fixed using adhesion by an adhesive, solder, and thelike. The semiconductor light emitting element 110 can also be directlyfixed onto the submount 24 without using the first and second gold bumps25 a and 25 b by the ball bonder.

Next, the n-side mounting electrode 24 a and the p-side mountingelectrode 24 b on the submount 24 are connected to electrodes providedon the container 22 side, not shown, by the bonding wire 26.

The first fluorescent layer 211 including the red fluorescent body isformed so as to cover the semiconductor light emitting element 110 andthe bonding wire 26. The second fluorescent layer 212 including a blue,green, or yellow fluorescent body is formed on this first fluorescentlayer 211.

As a method of forming each of the fluorescent layers, each of thefluorescent bodies dispersed into a resin raw material mixed solution isdropped, and the obtained solution is thermally polymerized by heattreatment to cure the resin. The resin raw material mixed solutioncontaining each of the fluorescent bodies is dropped, is left for awhile, and subsequently is cured. Thereby, particulates of each of thefluorescent bodies can sediment so that the particulates of each of thefluorescent bodies can be unevenly distributed in a lower portion ofeach of the first and second fluorescent layers 211 and 212. Thus, it ispossible to control the light emitting efficiency of each of thefluorescent bodies as appropriate. Subsequently, the cover 27 isprovided on the fluorescent layers, and the semiconductor light emittingdevice 201 according to this embodiment, i.e., a white LED, ismanufactured.

A part of the light generated in the semiconductor light emittingelement is directly extracted to the outside of the element. Anotherpart of the light is repeatedly reflected in the reflecting film, theinterface between the semiconductor layer and the substrate, theinterface between the substrate and open air, and the like and extractedfrom a surface of the element, a surface of the substrate, or a sidesurface of the element to the outside. A part of the light is absorbedby the n-side electrode or the like having a low reflection efficiency,and it causes reduced light extraction efficiency. Particularly, in thecase of the white LED having a combination of a near-ultraviolet LEDhaving a wavelength of the emitting light of 370 to 400 nm and afluorescent layer, in order to have a low absorption coefficient andavoid leakage of the near-ultraviolet light to the outside in thefluorescent layer for the near-ultraviolet LED, especially in the redfluorescent layer, it is necessary to apply more fluorescent layers. Asa result, returned light to the LED chip increases. The area of then-side electrode, which is an absorption region as viewed from thefluorescent layer side, cannot be ignored from a viewpoint of efficiencyof the white LED.

As the semiconductor light emitting element according to thisembodiment, the fluorescent layers are applied to a LED chip in whichthe n-side electrode having a low reflectance is reduced to a minimumarea necessary to reduce the operating voltage and the pad region havinga relatively wide area and the wider highly reflective region aresecured. Thereby, the efficiency of the white LED can be improved, andthe effect of this invention can be enhanced.

When the highly reflective insulating layer 60 (for example, adielectric multilayer) in the semiconductor light emitting elementaccording to this embodiment is optically designed in accordance with380 nm of an emission wavelength, high reflectivity to visible lightthat enters vertically to the highly reflective insulating layer 60 isnot shown. However, in the highly reflective insulating layer 60, awavelength region that shows high reflectivity is widened as theincident angle is inclined. The high reflectivity is shown inapproximately all of the regions of the visible light at the incidentangle inclined 30 degrees to the film surface.

Moreover, a reflective metal film having reflectivity to the visiblelight can also be disposed on the laminated structure body 10 s side ofthe n-side pad layer 41. As this reflective metal film, aluminum andrhodium can be used, for example. Namely, the n-side pad layer 41 isprovided on the laminated structure body 10 s side and can include alayer including at least one of aluminum, an aluminum alloy, rhodium,and a rhodium alloy.

Thereby, a component of the visible light emitted from the excitedfluorescent layers and returned toward the LED chip can efficiently bereflected and extracted to the outside of the semiconductor lightemitting element. Thereby, a phase of the light that reaches theaforementioned reflective metal film can also be controlled to form astructure that increases reflectivity.

Herein, a “nitride semiconductor” includes semiconductors of all thecompositions represented by the chemical formulaB_(x)In_(y)Al_(z)Ga_(1-x-y-z)N (0≦s x≦1, 0≦y≦1, 0≦z ≦1, x+y+z≦1) inwhich the composition ratio of x, y, and z is varied within the range.In the aforementioned chemical formula, moreover, the “nitridesemiconductor” also includes semiconductors further including a V groupelement other than N (nitrogen), and semiconductors further includingone of various dopants added in order to control a conductivity type orthe like.

Hereinabove, exemplary embodiments of the invention are described withreference to specific examples. However, the invention is not limited tothese specific examples. For example, one skilled in the art mayappropriately select specific configurations of components included insemiconductor light emitting elements and semiconductor light emittingdevices such as N-type semiconductor layers, p-type semiconductorlayers, light emitting layers, well layers, barrier layers, n-sideelectrodes, p-side electrodes, highly reflective insulating layers,dielectric laminated films, upper metal layers, mounting components,wavelength conversion portions, fluorescent bodies, and the like fromknown art and similarly practice the invention. Even modifications withrespect to shapes, sizes, qualities of materials, and crystal growthprocesses for the specific configuration of each of the components andwith respect to crystal growth processes are made by one skilled in theart, such practice is included in the scope of the invention to theextent that similar effects thereto are obtained.

Further, any two or more components of the specific examples may becombined within the extent of technical feasibility; and are included inthe scope of the invention to the extent that the purport of theinvention is included.

Moreover, semiconductor light emitting elements and semiconductor lightemitting devices practicable by an appropriate design modification byone skilled in the art based on the semiconductor light emittingelements and semiconductor light emitting devices described above asexemplary embodiments of the invention also are within the scope of theinvention to the extent that the purport of the invention is included.

Furthermore, various modifications and alterations within the spirit ofthe Invention will be readily apparent to those skilled In the art. Allsuch modifications and alterations should therefore be seen as withinthe scope of the invention.

1. A semiconductor light emitting element, comprising: a laminatedstructure body including an n-type semiconductor layer, a p-typesemiconductor layer, and a light emitting layer provided between then-type semiconductor layer and the p-type semiconductor layer; a p-sideelectrode provided in contact with the p-type semiconductor layer; ann-side electrode provided in contact with the n-type semiconductorlayer; a highly reflective insulating layer provided in contact with then-type semiconductor layer and having a higher reflectance to lightemitted from the light emitting layer than a reflectance of the n-sideelectrode to the light; and an upper metal layer provided on at least apart of the n-side electrode and on at least a part of the highlyreflective insulating layer and electrically connected to the n-sideelectrode, an area of a region of the n-side electrode in contact withthe n-type semiconductor layer being smaller than an area of a region ofthe highly reflective insulating layer sandwiched between the n-typesemiconductor layer and the upper metal layer.
 2. The element accordingto claim 1, wherein an area of a region of the n-side electrode facingthe upper metal layer is smaller than the area of the region of thehighly reflective insulating layer sandwiched between the n-typesemiconductor layer and the upper metal layer.
 3. The element accordingto claim 1, wherein the n-type semiconductor layer is exposed in anexposed region on a side of a first main surface of the laminatedstructure body, a part of the p-type semiconductor layer being removedin the exposed region, the n-side electrode and the highly reflectiveinsulating layer are provided in contact with the exposed n-typesemiconductor layer, the p-side electrode is provided in contact withthe p-type semiconductor layer on a side of the first main surface, andat least a part of the n-side electrode is provided closer to a side ofthe p-side electrode than the highly reflective insulating layer in aplane parallel to the first main surface.
 4. The element according toclaim 1, wherein a peak wavelength of the light is not less than 370nanometers but not more than 400 nanometers.
 5. The element according toclaim 1, wherein the laminated structure body further includes asubstrate made of sapphire and provided on a side of a second mainsurface opposite to the first main surface.
 6. The element according toclaim 5, wherein the laminated structure body is formed on the substratevia a single-crystal aluminum nitride layer.
 7. The element according toclaim 6, wherein the aluminum nitride layer has a first portion and asecond portion, the first portion being provided between the substrateand a second portion, the first portion has a carbon concentrationrelatively higher than a carbon concentration in the second portion. 8.The element according to claim 1, wherein the n-side electrode includesa transparent conductive film provided on a side of the n-typesemiconductor layer and having translucency to the light.
 9. The elementaccording to claim 8, wherein the transparent conductive film has ohmicproperty to the n-type semiconductor layer.
 10. The element according toclaim 1, wherein the upper metal layer includes a layer provided on aside of the laminated structure body and including at least one ofaluminum, an aluminum alloy, rhodium, and a rhodium alloy.
 11. Theelement according to claim 1, wherein the n-side electrode has ohmicproperty to the n-type semiconductor layer.
 12. The element according toclaim 1, wherein the n-side electrode includes at least one of silverand a silver alloy.
 13. The element according to claim 1, wherein thep-side electrode includes at least one of silver and a silver alloy. 14.The element according to claim 1, wherein the p-side electrode includesa silver contained film in contact with the p-type semiconductor layerand a platinum contained film stacked with the silver contained film.15. The element according to claim 1, wherein the upper metal layer isconnected to a connection member.
 16. The element according to claim 1,wherein the highly reflective insulating layer includes a plurality ofdielectric films alternatively laminated and having a differentrefractive index from each other
 17. The element according to claim 1,wherein the highly reflective insulating layer includes at least one ofoxide, nitride, or acid nitride of at least one of silicon (Si),aluminum (Al), zirconium (Zr), titanium (Ti), niobium (Nb), tantalum(Ta), magnesium (Ma), hafnium (Hf), cerium (Ce), zinc (Zn).
 18. Theelement according to claim 1, wherein the highly reflective insulatinglayer includes a silicon oxide contained film and a titanium oxidecontained film.
 19. A semiconductor light emitting device comprising: asemiconductor light emitting element; and a mounting component, thesemiconductor light emitting element being mounted on the mountingcomponent, the semiconductor light emitting element including: alaminated structure body including an n-type semiconductor layer, ap-type semiconductor layer, and a light emitting layer provided betweenthe n-type semiconductor layer and the p-type semiconductor layer; ap-side electrode provided in contact with the p-type semiconductorlayer; an n-side electrode provided in contact with the n-typesemiconductor layer; a highly reflective insulating layer provided incontact with the n-type semiconductor layer and having a higherreflectance to light emitted from the light emitting layer than areflectance of the n-side electrode to the light; and an upper metallayer provided on at least a part of the n-side electrodes and on atleast a part of the highly reflective insulating layer and electricallyconnected to the n-side electrode, an area of a region of the n-sideelectrode in contact with the n-type semiconductor layer being smallerthan an area of a region of the highly reflective insulating layersandwiched between the n-type semiconductor layer and the upper metallayer, the n-type semiconductor layer being exposed in an exposed regionon a side of a first main surface of the laminated structure body, apart of the p-type semiconductor layer being removed in the exposedregion, the n-side electrode and the highly reflective insulating layerbeing provided in contact with the exposed n-type semiconductor layer,the p-side electrode being provided in contact with the p-typesemiconductor layer on a side of the first main surface of the laminatedstructure body, the n-side electrode being provided on the first mainsurface of the laminated structure body, the mounting componentincluding a plurality of mounting electrodes, the first main surface ofthe laminated structure body and the mounting electrodes of the mountingcomponent being disposed to face each other, the upper metal layer beingelectrically connected to one of the mounting electrodes, and the p-sideelectrode being electrically connected to another one of the mountingelectrodes.
 20. The device according to claim 19, further comprising: awavelength conversion layer absorbing the light and emitting lighthaving a wavelength different from a wavelength of the light.